Torque tube assemblies for use with aircraft high lift devices

ABSTRACT

Example torque tube assemblies for use with aircraft high lift devices are described herein. An example torque tube assembly includes a torque tube having a first end and a second end opposite the first end. A first fitting is coupled to the first end and a second fitting is coupled to the second end. The first fitting is to be coupled to a first high lift device of an aircraft. The second fitting has a spline section. The torque tube assembly also includes a sliding spline shaft having a channel and a first yoke. The second fitting is slidably received within the channel. The torque tube assembly further includes a spline coupling having a second yoke, which is coupled to the first yoke of the sliding spline shaft to form a U-joint. The spline coupling is to be coupled to a second high lift device of the aircraft.

FIELD OF THE DISCLOSURE

This disclosure relates generally to torque tube assemblies and, moreparticularly, to torque tube assemblies with U-joints for use withaircraft high lift devices.

BACKGROUND

Aircraft employ high lift devices, sometimes referred to as auxiliaryairfoils, along the leading and trailing edges of the wings. Forexample, high lift devices along the leading edge of a wing are referredto as slats and high lift devices along the trailing edge of a wing arereferred to as flaps. The high lift devices are actuated to extendoutward from the wing to change the aerodynamic lift of the wing duringtakeoff and landing. Each of the high lift devices is actuated by one ormore drive mechanisms, which are coupled to ribs or support beams in thewing. In particular, each drive mechanism includes a pinion gear that isrotated to drive a rack coupled to the high lift device. As the piniongear is rotated, the rack is driven to move the high lift device along atrack, thereby extending the high lift device outward from the wing.Each pinion gear is in driving engagement with a geared rotary actuator(GRA). Each pinion gear and its respective GRA is interconnected with anadjacent (e.g., upstream and downstream) pinion gear and GRA via atorque tube. In other words, an aircraft typically employs a series oftorque tubes that translate torque to each of the driving mechanismsalong the leading or trailing edge of the wing. One motor may be used todrive one of the driving mechanisms, which thereby transfers torque toeach of the other driving mechanisms through the series of torque tubes.Therefore, each of the high lift devices may be controlled to move,simultaneously with the other high lift devices, between a stowedconfiguration and an extended configuration.

Known torque tube assemblies utilize bolted flanges or plates to couplea torque tube to a pinion gear or GRA. However, using flanges results ina relatively large rotational envelope, which requires a relativelylarge space to accommodate the rotating flanges. Further, in someinstances, the bolts of the flange can loosen, thereby reducing thestructural integrity of the torque tube. Also, as the wing flexes (e.g.,due to change in weight of the wing from decreasing fuel), the alignmentand distances between the driving mechanisms may change. This flexing ofthe wing causes additional forces and strain on the torque tubeassemblies.

SUMMARY

An example torque tube assembly disclosed herein includes a torque tubehaving a first end and a second end opposite the first end. A firstfitting is coupled to the first end and a second fitting is coupled tothe second end. The first fitting is to be coupled to a first high liftdevice of an aircraft. The second fitting has a spline section. Theexample torque tube assembly also includes a sliding spline shaft havinga channel. The second fitting is slidably received within the channel.The sliding spline shaft has a first yoke. The example torque tubeassembly further includes a spline coupling having a second yoke. Thesecond yoke of the spline coupling is coupled to the first yoke of thesliding spline shaft to form a U-joint. The spline coupling is to becoupled to a second high lift device of the aircraft.

An example method disclosed herein includes coupling a first fitting toa first end of a torque tube and a second fitting to a second end of thetorque tube. The first fitting has a first yoke, and the second fittinghas a radially extending spline section. The example method alsoincludes coupling the first yoke to a second yoke of a first splinecoupling to form a first U-joint, and inserting the splined section ofthe second fitting into a channel of a sliding spline shaft. The slidingspline shaft has a third yoke. The example method further includescoupling the third yoke to a fourth yoke of a second spline coupling toform a second U-joint, coupling the first spline coupling to a firstdrive shaft associated with first high lift device on an aircraft wing,and coupling the second spline coupling to a second drive shaftassociated with a second high lift device on the aircraft wing.

An aircraft disclosed herein includes a first geared rotary actuator(GRA) coupled to a wing of the aircraft and a second geared rotaryactuator (GRA) coupled to the wing. The first GRA has a first driveshaft and the second GRA has a second drive shaft. The example aircraftfurther includes a torque tube assembly coupled between the first driveshaft and the second drive shaft. The torque tube assembly has a firstportion fixedly coupled to the first drive shaft and a second portionfixedly coupled to the second drive shaft, the first portion axiallyslidably coupled to the second portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example aircraft in which example torque tubeassemblies and related methods disclosed herein may be implemented.

FIG. 2 is a partially sectioned view of an underside of a wing of theaircraft in FIG. 1 showing an example torque tube assembly constructedin accordance with teachings of this disclosure.

FIG. 3 is a perspective view of the example torque tube assembly of FIG.2 having a first example joint and a second example joint.

FIG. 4 is an enlarged perspective view of the first example joint ofFIG. 3 employing an example spline coupling to receive an example splinegear.

FIG. 5 is an exploded view of the first example joint of FIG. 4.

FIG. 6 is an isolated perspective view of the example spline coupling ofFIG. 4.

FIG. 7 is a cross-sectional view of the example spline coupling and theexample spline gear of FIG. 4.

FIG. 8 is an enlarged perspective view of the second example joint ofFIG. 4 employing an example sliding splined shaft.

FIG. 9 is a cross-sectional view of the second example joint of FIG. 8.

FIG. 10 is an exploded view of the second example joint of FIG. 8.

FIG. 11 is an exploded view of an example grease retainer that may beimplemented on the example sliding spline shaft of FIG. 8.

FIG. 12 is an example method for constructing and/or assembling anexample torque tube assembly.

The figures are not to scale. Instead, the thickness of the layers orregions may be enlarged in the drawings. In general, the same referencenumbers will be used throughout the drawing(s) and accompanying writtendescription to refer to the same or like parts. As used in this patent,stating that any part (e.g., a layer, film, area, region, or plate) isin any way on (e.g., positioned on, located on, disposed on, or formedon, etc.) another part, indicates that the referenced part is either incontact with the other part, or that the referenced part is above theother part with one or more intermediate part(s) located therebetween.Stating that any part is in contact with another part means that thereis no intermediate part between the two parts.

DETAILED DESCRIPTION

Disclosed herein are example torque tube assemblies and related methodsthat may be employed to mechanically transmit torque from a driver, suchas an output shaft of a motor or actuator of a high lift device, to adriven device, such as an input shaft of a subsequent (e.g., downstream,outboard) actuator of a high lift device. An example torque tubeassembly disclosed herein includes a first universal joint (U-joint)formed between a first torque tube fitting on one end of the torque tubeand a first spline coupling. The first spline coupling includes anintegral yoke that couples with a yoke on the first torque tube fittingto form the first U-joint. The yoke of the first torque tube fitting isintegral with the first torque tube fitting and, thus, fixedly attachedto the end of the torque tube. The spline coupling includes an openingwith splines (e.g., ribs) to receive a spline gear or shaft of a drivingmember (e.g., a first drive shaft). The driving member may be a pinionshaft and/or an output shaft of a geared rotary actuator (GRA), forexample.

The example torque tube assembly also includes a second torque tubefitting on the opposite end of the torque tube than the first torquetube fitting. The second torque tube fitting is slidably inserted into achannel in a sliding spline shaft. In particular, the second torque tubefitting includes splines that mesh with splines on the inside of thechannel, which enables the second torque tube fitting and the slidingspline shaft to slide axially relative to each other but not rotaterelative to each other. The sliding splined shaft includes a yoke thatforms a second U-joint with a yoke on a second spline coupling. Similarto the first spline coupling, the second spline coupling includes anopening with splines (e.g., ribs) to receive another spline gear orshaft of a driving member (e.g., a second drive shaft). Therefore, oneend of the torque tube assembly includes the first spline coupling,which may be coupled to a first drive shaft of a first GRA (e.g., anupstream driving member), and the other end of the torque tube assemblyincludes the second spline coupling, which may be coupled to a seconddrive shaft of a second GRA (e.g., a downstream driven member). As thespline gear of the first GRA rotates, the rotational power istransferred from the upstream drive shaft of the first GRA to thedownstream driven shaft of the second GRA.

In some examples, the first spline coupling and the second splinecoupling are fixedly coupled (e.g., via threaded fasteners) to the firstand second drive shafts, respectively, while the second torque tubefitting is slidably disposed within the sliding spline shaft. Therefore,one portion of the torque tube assembly (including the torque tube, thefirst torque tube fitting, and the first spline coupling) is fixedlycoupled to the aircraft and a second portion of the torque tube assembly(including the sliding spline shaft and the second spline coupling) isfixedly coupled to the aircraft, and the two portions are axiallyslidably coupled to each other. As such, the two portions of the torquetube assembly can translate axially relative to each other while stilltransferring rotational motion between the two drive shafts. Thus, asthe wing flexes, the portions of the torque tube assembly can bedisplaced axially (relative to each other) to reduce strain and force onthe torque tube assembly. Also, as the wing flexes, the U-joints enablethe torque tube assembly to move angularly with respect to the drivingmember (e.g., the first drive shaft and/or the spline gear) or thedriven member (e.g., the downstream drive shaft of the second GRA) whilestill transferring rotational motion between the two members.Furthermore, the ability to lengthen and shorten the torque tubeassembly is beneficial during installation, for example, when connectingthe two ends of the torque to be assembly to the first and second driveshafts (which, in some instances, have relatively tight tolerances).

In some examples, the second torque tube fitting includes two splinesections that are spaced apart from each other and that engage thesplines on the inside of the channel of the sliding spline shaft. Insome examples, one or more retaining bolts are screwed into the side ofthe sliding spline shaft and extend into the channel between the firstand second spline sections to prevent the second torque tube fitting andthe sliding spline shaft from becoming completely disconnected (e.g., inthe event of a failure of one of the parts). For example, if one portionof the torque tube assembly becomes disconnected from the aircraft, theretaining bolts prevent the second torque tube fitting fromdisconnecting from the sliding spline shaft and, thus, ensures thefailed portion remains connected to the aircraft via the other portionof the torque tube assembly. As such, the example retaining boltsprevent the part(s) of the torque tube assembly from potentiallydeparting from the aircraft and/or potentially causing damage to theaircraft.

In some examples, the torque tube assembly includes a grease retainerthat covers the opening where the second torque tube fitting is insertedinto the channel of the sliding spline shaft. The grease retainerprevents moisture and/or other unwanted material from accumulating inthe channel, which may otherwise cause corrosion in the channel andpotential seizure of the parts. Further, in some examples, grease isinjected into the channel to provide lubrication between the splines ofsecond torque tube fitting and the splines of sliding spline shaft. Thegrease retainer prevents the grease from escaping from the channel.

Example torque tube assemblies disclosed herein employ splineconnections instead of bolted plate/flange connections as seen in knowntorque tube assemblies. Spline connections provide excellent torquetransfer. Further, if the bolts of a known plate/flange connectionfails, for example, the plates/flanges fall apart and, thus, cannottransfer rotational energy therebetween. In example torque tubeassemblies disclosed herein, however, if the bolts fail, the splineconnections remain intact and, thus, the torque tube assembly cancontinue to transfer rotational energy (via the interaction between thesplines on each component). Additionally, in some examples, the exampletorque tube assemblies do not employ flanges (e.g., because theyimplement smaller envelope fittings such as EMF formed fittings) and,thus, the rotational envelope is relatively smaller than known torquetube assemblies. Also, in such examples, the risk of loosening flangebolts is eliminated. Further, example torque tube assemblies describedherein are less susceptible to dynamic imbalance, which may be caused bya missing bolt, for example. Example torque tube assemblies describedherein also utilize fewer fasteners than known torque tube assemblies.

FIG. 1 illustrates an example aircraft 100 in which examples disclosedherein may be implemented. In the illustrated example, the aircraft 100includes a fuselage 102, a first wing 104 coupled to the fuselage 102,and a second wing 106 coupled to the fuselage 102. The first and secondwings 104, 106 of the illustrated example have control surfaces such ashigh lift devices (e.g., auxiliary airfoils, slats, Kreuger flaps,trailing edge slats, etc.) that are located along the leading andtrailing edges of the first and second wings 104, 106, and which may bedisplaced or extended to change the aerodynamic lift of the aircraft100. When extended from the first wing 104, the high lift devicesincrease the effective size, curvature camber, and area of the firstwing 104, thereby increasing the lift of the first wing 104. Forexample, the first wing 104 includes a first slat 108, a second slat110, a third slat 112, a fourth slat 114, a fifth slat 116, a sixth slat118, and a seventh slat 120 located along a leading edge 122 and a flap124 located along a trailing edge 126. The first wing 104 may includemore or fewer slats and flaps. Additionally or alternatively, the firstwing 104 may include other control surfaces such as ailerons, spoilers,tabs, trailing edge slats, Kreuger flaps, etc. The second wing 106 mayinclude similar high lift devices but are not discussed to avoidredundancy.

In general, each of the slats 108-120 is deployed using two separate butcoordinated drive mechanisms or actuators, one on the inboard side andone on the outboard side of each of the respective slats 108-120. Therespective actuators of the slats 108-120 are coupled to each other andto an adjacent (e.g., an upstream or downstream) drive mechanism viaexample torque tube assemblies, as disclosed in further detail herein.In the illustrated example, a motor or power drive unit (PDU) 128 isemployed to drive an actuator for deploying the seventh slat 120. Anoutput of the actuator is operatively coupled via an example torque tubeassembly to another actuator for deploying the seventh slat 120, whichis operatively coupled via an example torque tube assembly to driveanother actuator for deploying the sixth slat 118, and so forth.Therefore, the PDU 128 provides driving power to all of the actuatorsvia the torque tube assemblies along the leading edge 122 of the firstwing 104 to deploy the high lift devices. In some examples, the PDU 128also provides driving power to all of the actuators for driving theslats on the second wing 106. As a result, all of the slats along theleading edges of the first and second wings 104, 106 may be deployedsimultaneously. Although the torque tube assemblies are described inrelation to the slats 108-120, it is understood that the examplesdisclosed herein may be similarly applied to any of the other high liftdevices (e.g., the trailing edge flaps).

FIG. 2 shows an underside of the leading edge 122 of the first wing 104between the first slat 108 and the second slat 110. As disclosed above,each of the slats 108-120 is actuated by two actuators (e.g., rack andpinion assemblies) that are mounted to ribs or supports in the firstwing 104, and the actuators are driven by the PDU 128 (FIG. 1). Anexample torque tube assembly 200 is illustrated that is employed totransfer rotational energy between one of the actuators of the secondslat 110 and one of actuators of the first slat 108. In particular, afirst actuator 202 is provided for moving the first slat 108. The firstactuator 202 includes a first rack 204 (e.g., a geared rack, a toothedrack), a first pinion gear 206 (e.g., a circular gear) that drives thefirst rack 204, and a first geared rotary actuator (GRA) 208 that drivesthe first pinion gear 206. The first pinion gear 206 is rotatablycoupled (e.g., mounted) to a first rib or support 210 of the first wing104. As the first pinion gear 206 rotates, the first rack 204 is drivenoutward, thereby extending the first slat 108 outward from the firstwing 104. In some examples, the first pinion gear 206 drives a sectorgear, which drives the first rack 204. The first pinion gear 206 iscoupled to and driven by the first GRA 208. The first GRA 208 has anupstream or input shaft 212 and a downstream or output shaft (e.g., ahigh lift device drive shaft). The first GRA 208 contains a gear train(e.g., a system of gears, a transmission) that may be used to change thegearing ratio between an input (e.g., the input shaft 212) and the firstpinion gear 206. In general, the PDU 128 (FIG. 1) rotates at arelatively fast speed (e.g., about 700 revolutions per minute (RPM)).The first GRA 208 reduces the rotational speed provided to the firstpinion gear 206 and, thus, increases the torque provided to the firstpinion gear 206. Similar to the first slat 108, the second slat 110includes a second actuator 216 having a second rack 218 and a secondpinion gear 220 driven by a second GRA 222 and operatively coupled to asecond rib or support 224. The second GRA 222 has an upstream or inputshaft 226 and a downstream or output shaft 228 (e.g., a high lift devicedrive shaft). To transfer rotational energy from the output shaft 228 ofthe second GRA 222 to the input shaft 212 of the first GRA 208, theexample torque tube assembly 200 is employed. As the output shaft 228 ofthe second GRA 222 rotates, the rotational power is transferred to theinput shaft 212 of the first GRA 208 via the torque tube assembly 200.Torque tube assemblies may be similarly employed between each of theactuators (e.g., rack and pinion assemblies) of each of the slats108-120. For example, the seventh slat 120 (FIG. 1), which is the mostinboard slat, includes an actuator (e.g., a pinion gear and GRA) that isdriven by the PDU 128 (FIG. 1). An output of the actuator is operativelycoupled to another actuator of the seventh slat 120 or to an actuator ofthe sixth slat 118 via a torque tube assembly, and so forth. Therefore,the input shaft 226 of the second GRA (and, thus, the second pinion gear220) is rotated via an upstream torque tube assembly operatively coupledto an inboard actuator of the second slat 110 or from actuator of thethird slat 112 (e.g., depending on how many actuators are used for eachof the slats 108-120). Similarly, the output shaft 214 of the first GRA208 may be operatively coupled to another actuator of the first slat 108via an example torque tube assembly.

FIG. 3 is an isolated view of the example torque tube assembly 200coupled between the output shaft 228 of the second GRA 222 and the inputshaft 212 of the first GRA 208. In the illustrated example, the torquetube assembly 200 includes a first joint 300 that couples a first end302 of a torque tube 304 to the output shaft 228 of the second GRA 222.The torque tube assembly 200 also includes a second joint 306 between asecond end 308 of the torque tube 304 and the input shaft 212 of thefirst GRA 208. The torque tube 304 may be any length desired. While inmany of the examples disclosed herein the torque tube assembly 200 isdescribe as being between drive shafts of two actuators, in otherexamples, one or more torque tube supports may be located between twoactuators or driving mechanisms (e.g., when a distance between twoactuators is relatively long). Therefore, in some examples, the torquetube assembly 200 may be split or divided into additional torque tubeassemblies. For example, instead of being coupled to an input/outputshaft (e.g., of an upstream or downstream actuator), the first and/orsecond joints 300, 306 of the torque tube assembly 200 may be coupled toa splined shaft at a torque tube support (e.g., a rib or support in thewing).

FIG. 4 is an enlarged view of the first joint 300 and FIG. 5 is anexploded view of the first joint 300. As shown in the illustratedexample, the first end 302 of the torque tube 304 is coupled to a firsttorque tube fitting 400 (referred to herein as the first fitting 400).In the illustrated example, the first fitting 400 is fixedly coupled tothe first end 302 of the torque tube 304 by an electromagnetic fittingor forming (EMF) process. An example EMF process for coupling an endfitting to an end of a torque tube is described in U.S. Pat. No.5,983,478, which is incorporated herein by reference in its entirety.EMF produces excellent rigid torque transmitting couplings between anend of a torque tube and an end fitting. In other examples, the firstfitting 400 may be coupled to the first end 302 of the torque tube 304using other mechanical and/or chemical techniques (e.g., welding,threaded fasteners, adhesives, etc.).

In the illustrated example, the first fitting 400 forms a first U-joint402 with a first spline coupling 404. As shown more clearly in FIG. 5,the first U-joint 402 includes a cross-journal 500 (e.g., a spider) andfour bearing caps 502 (which include an array of needle bearings) thatare coupled between a first yoke 504 (e.g., a fork) on the first fitting400 and a second yoke 506 on the first spline coupling 404. The firstfitting 400 has a wall or plate 508 and a first ear 510 and a second ear512 that extend from the plate 508 to form the first yoke 504. The firstand second ears 510, 512 have respective first and second openings 514,516 that are coaxially aligned along an axis 517. The first and secondopenings 514, 516 receive two of the bearing caps 502 of thecross-journal 500. In the illustrated example, the first yoke 504 isintegral with the first fitting 400 and, thus, form a substantiallyunitary piece or structure. However, in other examples, the first yoke504 and the first fitting 400 may be constructed of multiple pieces thatare operatively coupled to each other.

As illustrated in FIGS. 4 and 5, a first spline gear 406 is coupled tothe output shaft 228 of the second GRA 222 (FIG. 3). In some examples,the first spline gear 406 is integral with the output shaft 228 (e.g.,constructed as a single unitary part or component). The first splinegear 406 is coupled to the first spline coupling 404. In particular, thefirst spline gear 406 is received within a bore or opening 410 of thefirst spline coupling 404.

FIG. 6 is an isolated perspective view of the first spline coupling 404and FIG. 7 is a cross-sectional view of the first spline gear 406inserted into the first spline coupling 404. As shown in FIGS. 6 and 7,the first spline coupling 404 includes a wall or plate 600. An annularwall 602 extends from the plate 600 to define the opening 410, which isaligned with a longitudinal axis 604 of the first spline coupling 404.The first spline coupling 404 includes a first ear 606 and a second ear608 extending from the plate 600 that form the second yoke 506 (e.g., ina direction opposite to that of the annular wall 602). The first andsecond ears 606, 608 have respective first and second openings 610, 612that are coaxially aligned along an axis 614. In the illustratedexample, the axis 614 is perpendicular to the longitudinal axis 604. Thefirst and second openings 610, 612 receive two of the bearing caps 502(FIG. 5) of the cross-journal 500. As shown in FIG. 6, the opening 410of the first spline coupling 404 includes splines 616 (e.g., ribs,grooves, channels) around an inner surface 618 of the annular wall 602.In the illustrated example, the first spline coupling 404 (including thesecond yoke 506) is a substantially unitary piece or structure. However,in other examples, the first spline coupling 404 may be constructed ofmultiple pieces that are operatively coupled to each other.

In the illustrated example, the first spline coupling 404 includes threeholes or apertures 620, 622, 624 that extend through the annular wall602 into the opening 410 (e.g., in a direction perpendicular to thelongitudinal axis 604). The holes 620, 622, 624 are to receive threadedfasteners 518 (FIG. 5) to couple the first spline gear 406 to the firstspline coupling 404. In the illustrated example, the holes 620, 622, 624are equally spaced around the annular wall 602 (e.g., 120° degrees apartfrom each other). In other examples, the first spline coupling 404 mayinclude more or fewer holes and/or the holes may be spaced differently.

As shown in FIGS. 5 and 7, the first spline gear 406 has three holes(two of which are seen in FIG. 5 and labeled as 520 and 522), which areto be aligned with the holes 620, 622, 624 of the first spline coupling404. For example, as shown in FIG. 7, the first spline gear 406 isinserted into the opening 410 of the first spline coupling 404. Thethree holes of the first spline gear 406 are aligned with the respectiveholes 620, 622, 624 of the first spline coupling 404. The threadedfasteners 518 (FIG. 5) are threaded into the holes 620, 622, 624 andinto the corresponding holes of the first spline gear 406 to couple thefirst spline gear 406 and the first spline coupling 404. The threadedfasteners 518 may be bolts, screws, or any other suitable fasteningmechanisms.

FIG. 8 is an enlarged view of the second joint 306, FIG. 9 is across-sectional via of the second joint 306, and FIG. 10 is an explodedview of the second joint 306. In the illustrated example, a secondtorque tube fitting 800 (referred to herein as the second fitting 800,and which may also be referred to as a slider or spline) is coupled tothe second end 308 of the torque tube 304. Similar to the first fitting400 (FIG. 4), the second fitting 800 may be coupled to the second end308 of the torque tube 304 by an EMF process. In other examples, thesecond fitting 800 may be coupled to the second end 308 of the torquetube 304 via another mechanical and/or chemical fastening technique. Inthe illustrated example, the second torque tube fitting 800 includes ashaft 802 that is slidably received within a sliding spline shaft 804,discussed in further detail below.

In the illustrated example of FIGS. 8-10, the second joint 306 of thetorque tube assembly 200 includes the sliding spline shaft 804. Thesliding spline shaft 804 forms a second U-joint 806 with a second splinecoupling 808. In particular, the sliding spline shaft 804 includes athird yoke 810, the second spline coupling 808 includes a fourth yoke812, and a cross-journal 814 with four bearing caps 816 is disposedbetween the third and fourth yokes 810, 812.

As shown in FIGS. 9 and 10, a second spline gear 900, which is coupledto the input shaft 212 of the first GRA 208 (FIGS. 2 and 3), is receivedwithin and coupled to the second spline coupling 808. Thus, the secondspline coupling 808 is coupled to the input shaft 212 of the first GRA208. The second spline coupling 808 may be fixedly coupled to the secondspline gear 900 via threaded fasteners (e.g., three bolts), similar tothe connection between the first spline coupling 404 (FIGS. 5-7) and thefirst spline gear 406. In fact, in this example, the third yoke 810 ofthe sliding spline shaft 804 is substantially the same as the first yoke504 (FIG. 5) of the first fitting 400 (FIG. 5), the cross-journal 814and the bearing caps 816 are substantially the same as the cross-journal500 and the bearing caps 502 (FIG. 5), the second spline coupling 808 issubstantially the same as the first spline coupling 404 (FIGS. 5-7), andthe second spline gear 900 is substantially the same as the first splinegear 406 (e.g., the second spline gear 900 includes splines and openingsto received threaded fasteners). Thus, to avoid redundancy, adescription of the second U-joint 806 and the connection between thesliding spline shaft 804, the second spline coupling 808, and the secondspline gear 900 is not provided herein. Instead, the interested readeris directed to the description above relating to the first U-joint 402(FIG. 4) and the connection between the first fitting 400, the firstspline coupling 404, and the first spline gear 406 on the output shaft228. In some examples, instead of using the first and second splinegears 406, 900, the input and output shafts 212, 228 may instead besplined and sized to fit within the first and second spline couplings404, 808, respectively.

Therefore, in this example, the first spline coupling 404 (FIG. 4) (oneend of the torque tube assembly 200) is fixedly coupled to the outputshaft 228 (FIG. 3) of the second GRA 222 and the second spline coupling808 is fixedly coupled to the input shaft 212 of the first GRA 208. Insome examples, six threaded fasteners (e.g., bolts) are used to fixedlycouple the ends of the torque tube assembly 200 to the aircraft 100(three for the first spline coupling 404 and three for the second splinecoupling 808). Therefore, in some examples, only one screwdriver orsocket wrench may be needed to attach the ends of the torque tubeassembly 200 to the aircraft 100, as compared to known boltedflange/plate assemblies that require multiple screwdrivers or wrenches(one for the bolt heat and one for the nut) and which require additionalspace to fit the additional tools. In other examples, more or fewerthreaded fasteners may be used to couple the ends of the torque tubeassembly 200 to the aircraft 100.

The second fitting 800 is axially movable within a channel (e.g., anopening, a passageway, etc.) formed in the sliding spline shaft 804. Forexample, as illustrated in FIG. 9, a channel 902 (e.g., a splinedchannel) is formed between a first opening 904 (on one end of thesliding spline shaft 804) and a second opening 906 (on the opposite endof the sliding spline shaft 804, which opens between the ears of thethird yoke 810). The channel 902 and the first opening 904 are alsoshown in FIG. 10.

As illustrated in FIGS. 9 and 10, the sliding spline shaft 804 includessplines 908 (e.g., ribs, grooves, channels) on an inner surface of thechannel 902. The second fitting 800 includes first and second splinesections 910, 912 extending radially from the shaft 802. The first andsecond spline sections 910, 912 mesh with the splines 908 in the channel902, which enables the second fitting 800 and the sliding spline shaft804 to slide relative to each other while still transferring rotationalmotion between each other. In other words, the shaft 802 of the secondfitting 800 is axially slidable within the channel 902, but notrotatable within the channel 902. This sliding interaction enables thetorque tube assembly 200 to lengthen or shorten when the first wing 104(FIG. 2) of the aircraft 100 flexes, thereby reducing longitudinal loadson the torque tube assembly 200. For example, the torque tube assembly200 can be considered as two portions: a first portion including thefirst spline coupling 404, the first fitting 400, the torque tube 304,and the second fitting 800; and a second portion including the slidingspline shaft 804 and the second spline coupling 808. While the firstportion is connected to the aircraft 100 at the second GRA 222 and thesecond portion is connected to the aircraft 100 at the first GRA 208,the two portions can slide or move axially relative to each other,thereby enabling the torque tube assembly 200 (FIG. 2) to move axially(e.g., longitudinally) as the first wing 104 (FIG. 2) flexes or bends,while still transferring rotational motion between the second GRA 222 tothe first GRA 208. Additionally, the U-joints 300, 306 enable the torquetube assembly 200 to move angularly with respect the output shaft 228 ofthe second GRA 222 and the input shaft 212 of the first GRA 208 (e.g.,if the output shaft 228 and the input shaft 212 become misaligned).Therefore, the torque tube assembly 200 can be displaced angularlyand/or axially and, thus, less strain or adverse forces are imparted onthe torque tube assembly 200 than experienced in known assemblies.

In some examples, to prevent the second fitting 800 and the slidingspline shaft 804 from completely disconnecting from each other, theexample torque tube assembly 200 may include one or more retainingelements. The retaining element(s) may block, contact, and/or otherwiseprevent the second fitting 800 from completely exiting the slidingspline shaft 804 and becoming disconnected therefrom. In some examples,the retaining element(s) may be implemented as one or more bolt(s). Forexample, as illustrated in FIGS. 9 and 10, first and second retainingbolts 914, 916 are screwed into first and second openings 918, 920,respectively, in the sliding spline shaft 804. The first retaining bolt914 is also shown in FIG. 8. The first and second retaining bolts 914,916 extend into the channel 902 between the first and second splinesections 910, 912 (but, in some examples, do not engage the side of theshaft 802). If the second fitting 800 or the sliding spline shaft 804 ismoved relative to the other beyond a threshold distance (e.g., definedby the distance between the first and second spline sections 910, 912),the first or second spline section 910, 912 engages the first and/orsecond retaining bolts 914, 916. For example, should the first portionof the torque tube assembly 200 become disconnected from the aircraft100, the first portion remains connected to the second portion and,thus, the second portion (which is still connected to the aircraft 100)prevents the first portion from disconnecting from the aircraft 100. Thesame is true if the second portion became is disconnected from theaircraft 100. In some examples, the first and second spline sections910, 912 are spaced apart a distance that is greater than the axialflexing that occurs during normal operation (e.g., around 0.6 inches).As a result, during normal operation, neither of the first or secondspline sections 910, 912 contacts the first and second retaining bolts914, 916. Instead, the first and second retaining bolts 914, 916 areonly contacted if there is a failure of one or more parts of the torquetube assembly 200.

In the illustrated example, the first and second retaining bolts 914,916 are disposed on opposite sides of the sliding spline shaft 804(e.g., 180° apart). However, in other examples, the first and secondretaining bolts 914, 916 may be spaced differently. In the illustratedexample, two retaining bolts are implemented, which, in some examples,provides double redundancy (in case one retaining bolt fails). However,in other examples, only one retaining bolt may be used or more than tworetaining bolts may be used. Further, in other examples, anotherretaining element, such as a pin (e.g., a non-threaded pin), may be usedin addition to or as an alternative to the first and second retainingbolts 914, 916.

In some examples, grease is used in the channel 902 to lubricate thesliding interaction between the second fitting 800 and the slidingspline shaft 804. In some examples, grease may be injected into thechannel 902 via first and second grease ports 818, 820 (FIGS. 8 and 10).When grease is injected into the channel 902, the grease seepsthroughout the channel 902, which provides sliding lubrication betweenthe first and second spline sections 910, 912 and the splines 908 of thesliding spline shaft 804. In the illustrated example, the first andsecond grease ports 818, 820 are on opposite sides of the sliding splineshaft 804. The first and second grease ports 818, 820 are disposed alongthe same cross-section of the sliding spline shaft 804 as the first andsecond retaining bolts 914, 916 and are offset from the bolts by 90°. Inother examples, only one grease port may be provided or more than twogrease ports may be provided and/or the grease ports may be provided inother locations.

As illustrated in FIGS. 8-10, the torque tube assembly 200 includes agrease retainer 822 (e.g., a cover) to prevent the grease from escapingout of the first opening 904 of the channel 902, while still enablingthe second fitting 800 to move into and out of the channel 902. Thegrease retainer 822 is coupled to the sliding spline shaft 804 andcovers the first opening 904 of the channel 902 where the second fitting800 is inserted into the channel 902 (e.g., a junction of the firstportion and the second portion of the torque tube assembly 200). Thegrease retainer 822 has a first end 824 and a second end 826 oppositethe first end 824. The grease retainer 822 may be constructed of arelatively lightweight material such as nylon, for example. In otherexamples, the grease retainer 822 may be constructed of other materials.

As illustrated in FIGS. 9 and 10, the sliding spline shaft 804 includesa first rib 922 and a second rib 924 that form a groove 926. The greaseretainer 822 includes an inwardly extending collar 928 near the firstend 824 that fits within the groove 926. In some examples, a strap,band, cable, and/or other clamping member is wrapped around the outsideof the collar 928 to hold the grease retainer 822 on the sliding splineshaft 804. In other examples, no strap, band, cable, or clamping membermay be used. Instead, the grease retainer 822 may be rigid enough toremain seated in the groove 926 and, thus, remain coupled to the slidingspline shaft 804.

As illustrated in FIG. 9, the second end 826 of the grease retainer 822,which is disposed outward from (beyond) the end of the sliding splineshaft 804 (e.g., about 0.5 inches), extends inward toward the shaft 802of the second fitting 800. The second end 826 of the grease retainer 822includes a seal 930 (e.g., an o-ring) that provides sealing engagementbetween the grease retainer 822 and the shaft 802 to maintain the greasewithin the channel 902 (and/or contained within a small area outside ofthe channel 902). Further, the grease retainer 822 prevents moisture andother unwanted material from accumulating in the channel 902 andadversely affecting the surfaces of the splines (e.g., corroding thesplines).

In some examples, to prevent grease from escaping from the secondopening 906 of the channel 902 (on the right side in FIG. 9), a plug 932(shown in FIGS. 9 and 10) is inserted into the channel 902 from thesecond opening 906. In some examples, the plug 932 is press fit into thechannel 902. In other examples, the plug 932 may be coupled to thesliding spline shaft 804 via another mechanical and/or chemicalfastening technique.

As illustrated in FIGS. 9 and 10, in some examples, to preventover-pressurization of the channel 902, the sliding spline shaft 804includes first and second grease release ports 934, 936 (e.g., vents).The first and second grease release ports 934, 936 are relatively smallopenings or orifices. The grease release ports 934, 936 are sized toenable the grease to escape from the channel 902 if pressure inside ofthe channel 902 becomes too high. Otherwise, the pressure inside of thechannel 902 may cause the plug 932 and/or the grease retainer 822 toeject. While in the illustrated example two grease release ports areimplemented, in other examples, only one grease release port may beimplemented or more than two grease release ports may be implemented.Further, in other examples, the grease port(s) may be in other locationsand/or spaced differently. Further, as illustrated in FIGS. 8 and 10, insome examples, the grease retainer 822 includes one or more greaserelease ports 828 (two of which are referenced in FIG. 8 and two ofwhich are reference in FIG. 10), which are located near the second end826. The grease release ports 828 similarly release over-pressurized orexcess grease. In some examples, the grease retainer 822 includes fourgrease release ports 828 (e.g., spaced evenly around the grease retainer822). In other examples, the grease retainer 822 may include more orfewer grease release ports and/or the grease release ports may bedisposed in other locations.

In some examples, the grease retainer 822 is constructed of two piecesor parts that couple together to form the grease retainer 822. FIG. 11illustrates an example implementation of the grease retainer 822constructed of a first part 1100 a and a second part 1100 b. The firstand second parts 1100 a, 1100 b are the same type of part (i.e., havingthe same shape, size, dimension, features, etc.). The first and secondparts 1100 a, 1100 b are half cylinders that, when coupled, interlock toform a full cylinder. As such, during manufacture, only one type of partneeds to be manufactured (e.g., one mold can be used to make multipleparts), and two of the parts can be assembled to form the greaseretainer 822. Thus, the example grease retainer 822 can be manufacturedinexpensively by making multiples copies of the same part. To avoidredundancy, only the details of the first part 1100 a are describedbelow. However, it is understood that the second part 1100 b includesidentical features.

In the illustrated example, the first part 1100 a includes a first end1102 and a second end 1104, which form the first end 824 (FIG. 8) andthe second end 826 (FIG. 8), respectively, of the grease retainer 822when connected to the second part 1100 b. The first part 1100 a includesfirst a first groove 1106 at or near the first end 1102 to receive thefirst rib 922 (FIGS. 9 and 10) on the sliding spline shaft 804. Thefirst part 1100 a also includes a second groove 1108 to receive thesecond rib 924 (FIGS. 9 and 10) on the sliding spline shaft 804. Acollar portion 1110 is formed between the first groove 1106 and thesecond groove 1108. When the first and second parts 1100 a, 1100 b arecoupled, the collar portions form the collar 928 (FIGS. 9 and 10), whichis dimensioned to be received in the groove 926 on the sliding splineshaft 804. In the illustrated example, the first part 1100 a alsoincludes a third groove 1112 formed at or near the second end 1104. Whenthe first and second parts 1100 a, 1100 b are coupled, the third grooveforms a seal gland to receive the seal 930 (FIG. 9). One of the examplegrease release ports 828 is also shown in FIG. 11 on the first part 1100a.

To couple the first and second parts 1100 a, 1100 b, the first part 1100a includes a tab 1114 (e.g., a male extension) extending from one sideof the collar portion 1110 and a slot 1116 (e.g., a female opening toreceive a male extension, such as the tab 1114 of the second part 1100 b) formed on the opposite side of the collar portion 1110. When the firstand second parts 1100 a, 1100 b are coupled, the tab 1114 is to beinserted into the corresponding slot 1116 on the second part 1100 b, andthe slot 1116 receives the corresponding tab 1114 of the second part1100 b. To retain the first and second parts 1100 a, 1100 b together,the tab 1114 includes a clip 1118 (e.g., a ledge, a lip, a tang, etc.)that extends radially inward from the tab 1114 and rearward from the tab1114 (in a direction opposite the direction in which the tab 1114extends). Further, the slot 1116 includes a clip opening 1120 to receivethe corresponding clip 1118 on the second part 1100 b. When thecorresponding tab 1114 of the second part 1100 b is inserted into theslot 1116 of the first part 1100 a (and vice versa), the correspondingclip 1118 slides into the clip opening 1120 and prevents the first andsecond parts 1100 a, 1100 b from being pulled apart (unless the clips1118 are moved, for example, outward from the clip openings 1120). Inother examples, the grease retainer 822 may be constructed of a singleunitary piece (e.g., using a flexible material such as rubber) or morethan two pieces.

FIG. 12 is a flowchart representative of an example method 1200 that maybe implemented to construct and/or assemble an example torque tubeassembly, such as the example torque tube assembly 200 of FIG. 2. Atblock 1202, the first fitting 400 is coupled to the first end 302 of thetorque tube 304 and the second fitting 800 is coupled to the second end308 of the torque tube 304. In some examples, the first and/or secondfittings 400, 800 are coupled to the torque tube 304 via EMF. In someexamples, the torque tube 304 is constructed of aluminum and the firstand second fittings 400, 800 are constructed of steel. However, in otherexamples, the torque tube 304 and/or the first and/or second fittings400, 800 may be constructed of other materials. Further, in otherexamples, the first and second fittings 400, 800 may be coupled to thetorque tube 304 via other coupling techniques (e.g., welding, threadedfasteners, etc.).

At block 1204, the first yoke 504 of the first fitting 400 is coupled(e.g., via the cross-journal 500 and the bearing caps 502) to the secondyoke 506 of the first spline coupling 404 to form the first U-joint 402.At block 1206, the second fitting 800 is inserted into the channel 902of the sliding spline shaft 804. In particular, the first and secondspline sections 910, 912 are inserted into the splines 908 of thechannel 902. At block 1208, the third yoke 810 of the sliding splineshaft 804 is coupled (e.g., via the cross-journal 814 and the bearingcaps 816) to the fourth yoke 812 of the second spline coupling 808 toform the second U-joint 806.

At block 1210, the first spline coupling 404 is coupled to the aircraft100 via the output shaft 228 of the second GRA 222. For example, thefirst spline coupling 404 may be slid onto the first spline gear 406 toinsert the first spline gear 406 into the opening 410 of the firstspline coupling 404. In some examples, after the first spline gear 406is inserted into the first spline coupling 404, the threaded fasteners518 are screwed into the first spline coupling 404 and the first splinegear 406 to fixedly couple the first spline coupling 404 (and, thus, thefirst portion of the torque tube assembly 200) to the aircraft 100.

At block 1212, the second spline coupling 808 is coupled to the aircraft100 via the input shaft 212 of the first GRA 208. For example, aftercoupling the first spline coupling 404 to the first spline gear 406, thesliding spline shaft 804 (e.g., the second portion) may be moved towardthe torque tube 304 to compress or shorten the torque tube assembly 200.The second spline coupling 808 may be lifted to a position where it isaligned with the second spline gear 900, and the sliding spline shaft804 may be moved away from the torque tube 304 (lengthening the torquetube assembly 200) to slide the second spline coupling 808 onto thesecond spline gear 900. In other examples, the second spline coupling808 may be coupled to the input shaft 212 of the first GRA 208 first.After the second spline gear 900 is inserted into the second splinecoupling 808, one or more threaded fasteners may be screwed into thesecond spline coupling 808 and the second spline gear 900 to fixedlycouple the second spline coupling 808 (and, thus, the second portion ofthe torque tube assembly 200) to the aircraft 100.

At block 1214, the first and second retaining bolts 914, 916 areinserted into the channel 902 of the sliding spline shaft 804, whichprevents the second fitting 800 and the sliding spline shaft 804 frombecoming completely disconnected. For example, the first and secondretaining bolts 914, 916 may be screwed in the first and second openings918, 920, respectively, in the sliding spline shaft 804. At block 1216,the grease retainer 822 is coupled to the sliding spline shaft 804 tocover the first opening 904. In some examples, the grease retainer 822is constructed of two parts that connect (interlock). In some examples,a strap or band is placed around the grease retainer 822 to ensure thegrease retainer 822 does not become loose. In other examples, no strapor band may be used. At block 1218, grease may be injected into thechannel 902 through the first and/or second grease ports 818, 820. Thegrease provides lubrication between the first and second spline sections910, 912 of the second fitting 800 and the splines 908 of the channel902.

Although the example method 1200 is described with reference to theflowchart illustrated in FIG. 12, many other methods of manufacturingand/or assembly the example torque tube assembly 200 of FIG. 2 mayalternatively be used. For example, the order of execution of the blocksmay be changed, and/or some of the blocks described may be changed,eliminated, or combined. Similarly, additional operations may beincluded in the manufacturing and/or assembly process before, inbetween, or after the blocks shown in FIG. 12. Further, although thefirst spline coupling 404 is described as being coupled to the output ofa driving member and the second spline coupling 808 is described asbeing coupled to a driven member, it is understood that the torque tubeassembly 200 may be used in reverse. In other words, the second splinecoupling 808 may be coupled to a splined shaft of a driving member,which thereby drives the second spline coupling 808. Additionally,although the example torque tube assembly 200 is disclosed in relationto high lift devices of an aircraft, the example torque tube assembly200 may be used in any industry or application where rotational energyis transferred from one drive member (e.g., a drive shaft) to another.

From the foregoing, it will be appreciated that the above disclosedtorque tube assemblies and methods of making the same provide a moreflexible attachment between an upstream drive shaft and a downstreamdrive shaft in a wing of an aircraft. In particular, example torque tubeassemblies can move axially and angularly to adapt to any flexing and/orbending that may occur in a wing of an aircraft or other structure towhich the torque tube assemblies are connected. As a result, less forceor tension is concentrated along the torque tube assembly, therebyimproving the structural integrity of the torque tube assembly. Also,example torque tube assemblies are easier to install than known torquetube assemblies because the example torque tube assemblies can beshortened and lengthened while attaching the ends of the torque tubeassembly to the drive shafts. Further, example torque assemblies includea retaining feature that prevents parts from departing from the aircraftshould one portion of the torque tube assembly fail.

Although certain example methods, apparatus, and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus, and articles of manufacture fairly falling within the scopeof the claims of this patent.

What is claimed is:
 1. A torque tube assembly comprising: a torque tubehaving a first end and a second end opposite the first end, a firstfitting coupled to the first end and a second fitting coupled to thesecond end, the first fitting to be coupled to a first high lift deviceof an aircraft, the second fitting having a spline section; a slidingspline shaft having a channel, the second fitting slidably receivedwithin the channel, the sliding spline shaft having a first yoke; and aspline coupling having a second yoke, the second yoke of the splinecoupling coupled to the first yoke of the sliding spline shaft to form aU-joint, the spline coupling to be coupled to a second high lift deviceof the aircraft.
 2. The torque tube assembly of claim 1, furtherincluding a retaining bolt extending into the channel, the retainingbolt to prevent the second fitting from sliding beyond a thresholddistance into or out of the channel of the sliding spline shaft.
 3. Thetorque tube assembly of claim 2, wherein the spline section is a firstspline section, the second fitting further including a second splinesection spaced apart from the first spline section, the retaining boltextending into the channel between the first and second spline sections.4. The torque tube assembly of claim 1, wherein the sliding spline shaftincludes a grease port to enable grease to be injected into the channel.5. The torque tube assembly of claim 1, further including a greaseretainer coupled to the sliding spline shaft and covering an opening ofthe channel to maintain grease in the channel of the sliding splineshaft.
 6. The torque tube assembly of claim 5, wherein the greaseretainer includes a first part and a second part, each of the first partand the second part including a tab and a slot that is to mate with thecorresponding tab and slot of the other one of the first part or thesecond part.
 7. The torque tube assembly of claim 1, wherein the slidingspline shaft includes a grease release port.
 8. The torque tube assemblyof claim 1, wherein the spline coupling is a first spline coupling, theU-joint is a first U-joint, and the first fitting on the torque tube hasa third yoke, and further including a second spline coupling with afourth yoke, the fourth yoke of the second spline coupling coupled tothe third yoke of the first fitting to form a second U-joint, the secondspline coupling to be coupled to the first high lift device of theaircraft.
 9. The torque tube assembly of claim 8, wherein the first andsecond spline couplings include apertures to receive threaded fastenersto fixedly couple the first and second spline couplings to drive shaftsof the first and second high lift devices, respectively.
 10. A methodcomprising: coupling a first fitting to a first end of a torque tube anda second fitting to a second end of the torque tube, the first fittinghaving a first yoke, the second fitting having a radially extendingspline section; coupling the first yoke to a second yoke of a firstspline coupling to form a first U-joint; inserting the splined sectionof the second fitting into a channel of a sliding spline shaft, thesliding spline shaft having a third yoke; coupling the third yoke to afourth yoke of a second spline coupling to form a second U-joint;coupling the first spline coupling to a first drive shaft associatedwith first high lift device on an aircraft wing; and coupling the secondspline coupling to a second drive shaft associated with a second highlift device on the aircraft wing.
 11. The method of claim 10, furtherincluding inserting a retaining bolt into the sliding spline shaft thatextends into the channel.
 12. The method of claim 10, further includingcoupling a grease retainer to an end to the sliding spline shaft tocover an opening of the channel, the grease retainer including a firstpart and a second part that interlock to form the grease retainer, thefirst part and the second part being a same type of part.
 13. The methodof claim 10, further including injecting grease into the channel througha grease port on the sliding spline shaft.
 14. The method of claim 10,wherein coupling the first spline coupling to the first drive shaftincludes sliding the first spline coupling onto a first spline gear onthe first drive shaft and fixedly coupling the first spline coupling tothe first spline gear via a first threaded fastener, and whereincoupling the second spline coupling to the second drive shaft includessliding the second spline coupling onto a second spline gear on thesecond drive shaft and fixedly coupling the second spline coupling tothe second spline gear via a second threaded fastener.
 15. The method ofclaim 10, wherein coupling the first fitting to the first end of thetorque tube includes electromagnetically forming the first end of thetorque tube onto the first fitting, and wherein coupling the secondfitting to the second end of the torque tube includeselectromagnetically forming the second end of the torque tube onto thesecond fitting.
 16. An aircraft comprising: a first geared rotaryactuator (GRA) coupled to a wing of the aircraft, the first GRA having afirst drive shaft; a second geared rotary actuator (GRA) coupled to thewing, the second GRA having a second drive shaft; and a torque tubeassembly coupled between the first drive shaft and the second driveshaft, the torque tube assembly having a first portion fixedly coupledto the first drive shaft and a second portion fixedly coupled to thesecond drive shaft, the first portion axially slidably coupled to thesecond portion.
 17. The aircraft of claim 16, wherein the first portionof the torque tube assembly includes: a torque tube having a first endand a second end opposite the first end; a first fitting coupled to thefirst end, the first fitting having a first yoke; a second fittingcoupled to the second end; and a first spline coupling with a secondyoke, the first yoke of the first fitting coupled to the second yoke ofthe first spline coupling to form a first U-joint, the first splinecoupling fixedly coupled to the first drive shaft.
 18. The aircraft ofclaim 17, wherein the second fitting includes a radially extendingspline section, and wherein the second portion of the torque tubeassembly includes: a sliding spline shaft having a splined channel, theradially extending spline section of the second fitting slidablyreceived within the splined channel, the sliding spline shaft having athird yoke; and a second spline coupling with a fourth yoke, the thirdyoke of the sliding spline shaft coupled to the fourth yoke of thesecond spline coupling to form a second U-joint, the second splinecoupling fixedly coupled to the second drive shaft.
 19. The aircraft ofclaim 16, wherein the first and second portions of the torque tubeassembly are coupled to the first and second drive shafts, respectively,via threaded fasteners.
 20. The aircraft of claim 16, further includinga grease retainer covering a junction between the first and secondportions of the torque tube assembly.